Method of preparing mixed-salt containing lubricants



Oct. 20, 1959 A. BEERBOWER ETAL 2,909,485

METHOD OF PREPARING MIXED-SALT CONTAINING LUBRICANTS Filed Aug. 9, 1957.

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8 F w V NIETHOD OF PREPARING MIXED-SALT CONTAINING LUBRICANTS AlanBeerbower and William H. Gay, Baltimore, Md., as-

signors to Esso Research and Engineering Company, a corporation ofDelaware Application August 9, 1957, Serial No. 677,308

Claims. (Cl. 252-39) This invention relates to an improved process forpreparing mixed-salt containing lubricants. Particularly, the inventionrelates to an improved method of preparing lubricating compositionscontaining metal salts of intermediate and/or high molecular Weightcarboxylic acids with metal salts of low molecular weight fatty acids.

Lubricants containing the mixed-salts of high and/or intermediatemolecular weight fatty acids with salts of low molecular weight fattyacids have been finding increasing applications in industry because oftheir excellentjload-carrying'and anti-wear properties. For example:fluid lubricants of this type have been found to be particularly usefulin the lubrication of the upper cylinders of marine diesel engines;Whereas the solid grease type lubricants are useful for a variety ofindustrial applications. Previously, this type of lubricant had beencommercially prepared by coneutralizing with a metal base, an oildispersion of the low molecular Weight fatty acid and the higher fattyacids. However, lubricants prepared by simple mixing and heating of thecomponents,'using lime as the metal base'and acetic acid as the lowmolecular Weight acid, contain an undesirable abrasive grit. The use ofanhydrous calcined barium hydroxide, strontium hydroxide or magnesiumhydroxide with acetic acid can also result in grit formation. Severalmethods have-been suggested for overcoming the grit problem. For exampleone method is by highly agitating an oil-lime-higher fatty acid slurryas the acetic acid is added; another is by circulating anoil-lime-higherfatty acid slurry and then very slowly adding the acetic acid. However,a new method of forming these lubricants has been found, which does notrequire a high degree of agitation or circulating-equipment, in ordertoform gritfree lubricants. In this new method acetic 'acid anhydride isutilized in placeof acetic acid. Furthermore, by using acetic anhydride,a much simpler process for forming the lubricant may be employed becauseof the higher heat of reaction of the acetic anhydride as compared tothe acetic acid and also because of the lesser amount of water that isformed during the reaction. Also, the acetic anhydride forms a superiorfluid lubricant in that it has a lower viscosity for a given ashcontent. Similar 2 two types of fatty acids in any proportion. The fluidlubricants are best prepared by heating the mixed-salt material totemperatures of about 300 to 350 F., while the greases are best preparedby heating to about 430 to 700 R, where true complexing occurs. However,the

. fluid lubricants can also be prepared at these higher temperatures,i.e. 430 F. and above, while the greases may also be prepared at thelower temperatures, ie less than 430 F.

The high molecular weight carboxylic acids contemplated in thisinvention include the saturated and unsaturated grease-making fattyacids that arecommonly known in the art. In general, these fatty acidshave from 12 to about 30 carbon atoms, preferably about 14 to 22 carbonatoms per molecule, having saponification values I of from about 300 to150. Suitable fatty acids include lubricants may be prepared by usingthe anhydrides of prise in a molar ratio about 5 to 40, e.g. 5 to 12moles of alkaline earth metal salt of a C to C fatty-acid anhydride permole of alkaline earth metal salt of the higher fatty acids. The higherfatty acids may consist entirely ofintermediate molecularweight fattyacid or entirely of high molecular-weight fatty acid or blends of thesemyristic acid, palmitic acid, stearic acid, the various hydroxy stearicacids, oleic acid, arachidic acid, behenic acid andthe like. Naturallyoccurring fatty acids such as fish oil acids, tallow acid, etc. may alsobe utilized directly or after hydrogenation to decrease any undesirablyhigh degree of unsaturation. Mixtures of these high molecular weightfatty acids, e.g. hydrogenated fish oil acids with oleic acid, in anyproportions, are also operable, as are fractions obtained bydistillation, extraction or crystallization.

Intermediate molecular weight fatty acids operable for the saltformation include those aliphatic, saturated or unsaturated,unsubstituted, monocarboxylic acids contain.- ing 7 to 12 carbon atomsper molecule, e.g., capric, caprylic, nonanoic acids, etc. 7

The metal component of the mixed-salt thickeners of this invention maybe an alkaline earth metal such as calcium, strontium, barium andmagnesium. Mixtures of the grease-forming metals may be employed if de-,sired. The metals are usually reacted with the acids in the form ofmetal bases, such as hydroxides or oxides. Calcium is preferred.

- The lubricating oil used in the compositions of the invention may beeither a mineral lubricating oil, or a .synthetic lubricating oil, orboth. Synthetic'lubricating oils which may be used include esters ofmonobasicacids (e.g. C Oxo alcohol ester ofC Oxo acid), esters ofdibasic acids (e.g. di-Z-ethyl hexyl sebacate), esters of glycols (e.g.C Oxo acid diester of tetraethylene glycol), complex esters, esters ofphosphoric acid, halocarbon oils, sulfite esters, silicone oils,carbonates, polyglycol-type synthetic oils, etc., or any mixturethereof. Various other additives may also be added to the lubricatingcomposition in amounts of about 0.1 to 10.0 weight percent, based on thetotal weight of the composition. For example, detergents such as calciumpetroleum sulfonate; oxidation inhibitors such asphenyl alphanaphthylamine; corrosion inhibitors such as sorbitan monooleate; pourdepressants; dyes; other grease thickeners andthelikemaybeadded. v v

The fluid lubricant compositions of this invention .can be prepared byblending together the higher fatty acid (or the preformed higher fattyacid salt) and acid an-' hydride. A neutralizing amount of the dry metalbase is dispersed in a portion of the lubricating oil to form r a slurrywhich may be slightly warmed to atem'perature of about to F. The mixedacids are then added to the slurry. Alternatively, the higher fatty acidmay be incorporated in the metal base-oil slurry and then the acidanhydride is added. In either case, the heat'of reaction will'usually besufiicient such that a finishing temperature is reached, say about 300to 350911, e.'g. 310 to 340 F. This method may be conducted batchwise orpreferably in'continuous equipment. 1 .1 l The compositions for solidhightemperature greases can best be prepared in pressure equipment.Here, both Patented Oct. 20,1959,

the acid anhydride and the slurried metal base portion are separatelypreheated to temperatures of about 200 to 325 F., e.g. 225 to 300 F2After mixing, the heat of reaction will then usually be sufficient thata finishing temperature is reached, say about 430 to 700 F., e.g.,-430to 600 F. External heating may be applied, but generally will not benecessary due to the heat of reaction of the acid anhydride with themetal base. In this way, complex mixed-salt thickeners requiring hightemperatures can be formed without the use of the more costly fireheated, Dowtherm heated, or other high temperature kettles. Formation ofthe thickeners in a pressure system is particularly preferred, as itconserves heat and retains the water of reaction as steam which aids inobtaining a more complete reaction.

After the completion of the reaction, additional oil, if any, is addedalong with any additive material. The mixture may then be homogenized bypassing through a Gaulin homogenizer or a Charlotte mill, followed bysubsequent cooling to room temperature.

However, While a batch or open kettle system may be used in preparingeither the fluid or grease lubricants, the acid anhydride compositionadapts itself well to a simple continuous or semi-continuous pressuresystem which can be carried out as follows:

Referring now to the drawing, which represents a pre ferred method ofcarrying out the invention, the metal base and a portion of thelubricating oil (for example, one-third to one-sixth of the total oilused) are slurried together and heated to about 200 to 325 F. in a mixer10. This slurry can be pumped through line 11 at a measured rate througha metering pump 12, to a mixer 13 (e.g. a centrifugal pump). At the sametime, a measured rate of acid anhydride is pumped from the storage tank14 through the line 15 by means of the pump 16 into the mixer 13, wherethe two streams are intimately mingled and the reaction begins. Theresulting mixture may then pass through the line 17 into the bottom of apressure reactor 18 which holds the mixture for about 1 to minutes andwill operate at temperatures of about 300 and higher (about 435 to 580F. when greases are made), the heat being supplied by the reaction ofthe acid anhydride with the metal base, and the exact temperaturedepending on the proportion of ingredients and the amount of oil used.The reaction product is drawn off from the top of the reactor 18 throughline 19. Additional lubricating oil, which may also contain additivematerials, supplied from the storage tank 20 by means-of the pump 21,also passes into the line 19 to dilute the above-mentioned reactionmixture. This diluted mixture then passes through the control valve 22in the line 19 into a dehydrater 23, such as a Cornell homogenizer, orother vacuum chamber where the grease is subjected to vacuums of aboutto 29 inches of mercury, such that the Water is flashed off as steam.The grease then passes out of the dehydrater 23, through line 24 and isready for packaging or further finishing. A pump is usually required tolift the grease out of the vacuum, although the Cornell homogenizer doesthis by centrifugal force.

The invention will be further understood by the following examples whichinclude preferred embodimentsof the invention.

EXAMPLE I(A) Abase composition was prepared as follows: 30 grams of dryhydrated lime (i.e. Ca(OH) 10 grams of hydrogenatedfish oil acids havingan iodine value of 2.0 and consisting by weight of saturated fatty'acidsas follows: C14 C16, C18, and C22; and 10 grams of hydrogenated castoroil comprising the glycerides of l2-hydroxystearic acid and having aniodine value of 1.5; were dissolved in about 68 grams of a mineral oilhaving a viscosty of 600 SUS at 100 F. This mixture was heated up to 220F. to dissolve the acids, then cooled and 342 grams of the same oil wereadded. 40 grams of acetic acid were then mixed into the base compositionand the temperature increase due to the heat of reaction was measured.Upon cooling the material was inspected.

EXAMPLE I(B) Example I(A) was repeated except that 35.3 grams of aceticanhydride were used in place of the 40 grams of acetic acid.

Results of these tests are summarized in the following table.

As seen from the above examples, the acetic anhydride formed a grit-freelubricant while the acetic acid formed grit. The gel of Example I(A) wasdue to a high water content of 2.4%, while Example I(B) with 1.2% waterwas already half dehydrated and correspondingly fluid. The diiference of43 F. in temperature rise indicates the amount of cooking time to besaved in an open batch process, to which may be added the time saved bynot having to evaporate 1.2% of water.

However, the greatest savings are gained in the formation of lubricantscontaining a mixed-salt complex formed at above 435 F., particularlywhen using a pressure process, which process may be either batch orcontinuous. Using acetic anhydride as an example, if the initial mixturecontaining one-sixth of the oil is reacted, the temperature increase dueto the heat of reaction becomes 335 F. At an initial temperature of 220F. of the oilfatty acid-acetic anhydride slurry, the resulting reactionmixture (after addition of dry Ca(OH) has a temperature of 555 F., wellabove the minimum of 435 F. for complex formation. On the other hand,acetic acid will yield a final temperature of only 430 F. under theseconditions, By thus using acetic anhydride, the entire operation thenbecomes self-cooking except for the initial preparation of the base at220 R, which requires only exhaust steam heat thereby avoiding the useof fire, electric or Dowtherm heat. After this, water may be removed andthe batch cooled by bleeding off steam, before or after oiling with theremaining five-sixths of the oil.

The following example illustrates both a continuous system of formingthe mixed-salt concentrate, and the use of the acetic anhydride informing a fluid type lubricant.

EXAMPLE II An acid feed at 77 F. consisting of 3000 grams (78 weightpercent) of acetic anhydride and 860 grams (22 weight percent) ofWecoline AAC acid (28 weight percent caprylic, 56 weight percent capricand 16 weight percent lauric acid) was fed under pressure at the rate of21 grams a minute into a mixer (a Gould centrifugal pump with a threeinch open rotor operating at 1750 rpm). Simultaneously, a slurry feed(77 F.) consisting of 2,625 grams (20 weight percent) of dry hydratedlime and 10,500 grams (80 weight percent) mineral lubricating oil havinga viscosity of 80 SUS at 210 F. was also fed under pressure into themixer at an average rate of 71.4 grams per minute. Flow through thecentrifugal pump was the reverse of normal so as to maximize tubulence.The outlet temperature from the mixer ranged between 305 and 357 F. andaveraged about 327 F. The product issued from the mixer through apressure control valve set at 80 p.s.i.g., which ham permitted flashingmost of the water of reaction into steam. A temperature rise of up to280 F. was due to the heat of reaction, except for a small amount ofheat due to mixing energy. Approximately 4.9 grams of water per minutewere thus flashed oif, leaving an output of 86.5 grams per minute of theremaining reaction mixture. This nearly dry reaction product was thenpassed into a steam kettle and accumulated. When all the reactionproduct had accumulated in the kettle, it was then heated to 250 F. forabout 4 hours to reduce the water content from 0.6 to 0.4 weight percentafter which a total of 67,067 additional grams of oil were added alongwith 135 grams of phenyl alpha naphthylamine to form the finishedlubricant. The product was then milled twice by passing through an ND-1Charlotte mill and finally cooled to room temperature.

The above experiment was repeated using acetic acid in place of theacetic anhydride (the number of moles of acetic acid being used beingequal to the number of moles of acetic anhydride originally used). Thecritical results of this experiment are summarized in Table II whichfollows.

As seen from the above table, the use of the acetic anhydride gave amuch larger temperature rise in the mixer (i.e. reactor), thussubstantially reducing the time and amount of heat required in the steamkettle to obtain the desired degree of dehydration. Also, the use of theacetic anhydride resulted in a more fluid lubricant having a lowerviscosity and yet having the same metal content as that prepared fromthe acetic acid.

What is claimed is:

1. A method of preparing a lubricating oil composition containing 4 to30 weight percent of a mixed-salt material comprising alkaline earthmetal salt of a C to C fatty acid and alkaline earth metal salt of a Cto C fatty acid, in a molar ratio of about 5 to 40 moles of said C to Cfatty acid salt per mole of said O; to C fatty acid salt, whichcomprises, reacting with an alkaline earth metal base in a lubricatingoil menstruum, said C to C fatty acid and a C to C fatty acid anhydride.

2. A method according to claim 1, wherein said reaction mixture isheated to temperatures of about 300 F. to 700 F.

3. A method according to claim 1, wherein said fatty acid anhydride isacetic acid anhydride.

4. A method according to claim 3, wherein said alkaline earth metal iscalcium.

5. A method of forming a fluid lubricant comprising lubricating oil andabout 8 to 16 weight percent of a mixed-salt material comprisingalkaline earth metal salt of a C to C fatty acid and allkaline earthmetal salt of a C to C fatty acid, in a molar ratio of about 5 to 40moles of said C to C fatty acid salt per mole of said O, to C fatty acidsalt, which comprises forming a slurry of a portion of the lubricatingoil, alkaline earth metal base, and a material selected from the groupconsisting of C to C fatty acid and alkaline earth metal salt of C to Cfatty acid, mixing a C to C fatty acid anhydride into said slurry, theproportion of lubricating oil and other ingredients being such that afinishing temperature of about 300 to 350 F. is obtained by the heat ofreaction, adding the remainder of said oil and then cooling to form saidlubricant.

6. A method according to claim 5, wherein said alkaline earth metal iscalcium, and said acid anhydride is acetic acid anhydride.

7. A method of forming a lubricant containing 4 to 30 weight percent ofa mixedsalt material comprising alkaline earth metal salt of a C7 to Cfatty acid and alkaline earth metal salt of a C to C fatty acid, in amolar ratio of about 5 to 40 moles of said C to C fatty acid salt permole of said O; to C fatty acid salt, which comprises forming a slurryof: about one-third to one-sixth of the lubricating oil, the C to Cfatty acid and an alkaline earth metal base; preheating said slurry toabout 200 to 325 F., mixing with said preheated slurry a C to C fattyacid anhydride whereby the heat of reaction raises the temperature ofthe reaction mixture to 430 'F. to 700 F., adding the remainder of thelubricating oil and dehydrating to form said lubricant.

8. A method according to claim 7, wherein said reaction is carried outin a pressure system.

9. A method according to claim 7, wherein said lubricating oil ismineral oil.

10. A method according to claim 9, wherein said alkaline earth metal iscalcium, and said fatty acid anhydride is acetic acid anhydride.

References Cited in the file of this patent UNITED STATES PATENTS2,417,428 McLennan Mar. 18, 1947 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 2909.485 October 2O 1'95,

Alan Beerhower et a1.

pears in the printed specification It is hereby certified that error aprrection and that the said Letters of the above numbered patentrequiring co Patent should read as corrected below.

Coiumn 5, line 52', for "C read C Signed and sealed this 25th day ofApril 1961,

(SEAL) Atteat:

ERNEST W. SWIDER DAVID LADD Atteeting Oflicer Commissioner of Patents

5. A METHOD OF FORMING A FLUID LUBVRICANT COMPRISING LUBRICATION OIL AND ABOUT 8 TO 16 WEIGHT PERCENT OF A MIXED-SALT MATERIAL COMPRISING ALKALINE EARTH METAL SALT OF A C7 TO C30 FATTY ACID AND ALKALINE EARTH METAL SALT OF A C2 TO C3 FATTY ACID, IN A MOLAR RATIO OF ABOUT 5 TO 40 MOLES OF SAID C2 TO C3 FATTY ACID SALT PER MOLE OF SAID C7 TO C30 FATTY ACID SALT, WHICH COMPRISES FORMING A SLURRY OF A PORTION OF THE LUBRICATING OIL, ALKALINE EARTH METAL BASE, AND A MATERIAL SELECTED FROM THE GROUP CONSISTING OF C7 TO C30 FATTY ACID AND ALKALINE EARTH METAL SALT OF C7 TO C30 FATTY ACID, MIXING A C2 TO C3 FATTY ACID ANHYDRIDE INTO SAID SLURRY, THE PROPORTION OF LUBRICATING OIL AND OTHER INGREDIENTS BEING SUCH THAT A FINISHING TEMPERATURE OF ABOUT 300 TO 350*F. IS OBTAINED BY THE HEAT OF REACTION, ADDING THE REMAINDER OF SAID OIL AND THEN COOLING TO FORM SID LUBRICANT. 